The copper amine oxidase from bovine plasma has recently been found to contain 2,4,5-trihydroxyphenylalanine (topa) as the active site, redox cofactor. This discovery opens up many new avenues of research. Specific aims for the projected granting period include: (1) Establishing the generality of topa as a redox cofactor in copper amine oxidases from a variety of sources (bacteria, yeast and mammalian tissue); (2) Determining the sequences of topa containing peptides, to ascertain the presence and nature of a consensus sequence; (3) Identifying the DNA sequence encoding the topa cofactor; (4) Establishing the pathway of topa biogenesis; (5) Elucidating the physical and chemical properties of topa model compounds; and (6) Pursuing the reactivity and catalytic properties of topa at the active site of bovine plasma amine oxidase.